Sorry but you can't do a custom field formula for a built-in field such as the % Complete field.
Your "status" column appears to apply to a single all-encompassing task. It appears you's making a routine process more difficult. If instead you create a flow of tasks (e.g. start milestone, create draft, perform internal review, etc.), then it becomes a simple matter of taking credit as each major element is completed.
If the above suggestion doesn't work for you then perhaps a more detailed explanation of exactly what you are trying to accomplish will help us help you.